The Role of the Expert Witness By Orlando Pownall QC and Darryl Lockwood, from insidetime issue August 2010 Cases involving allegations of murder are more likely to involve expert evidence than most others. Because the allegation is so serious the prosecution are likely to be willing to incur the costs involved. The defence must not be disadvantaged by second rate resources; solving the classic ‘whodunnit’ can be influenced by such evidence. However phone schedules and cellsite evidence are now also commonplace in more mundane cases. With the recent – dramatic advances in technology, experts now cover a vast spectrum of issues. They can be used for identification purposes (fingerprinting, DNA, fibre analysis, handwriting, voice analysis); to re-create the crime scene (blood distribution, nature and location of injuries); assess the physical and mental state of the parties (toxicology, pathology, psychiatry and psychology) and even trace the movements of the parties in the period leading up to and including the assault . The proper calling and testing of expert evidence is, however, potentially fraught with problems. Many a sound case has come to grief as the expert evidence upon which it is based has proved unsound, unreliable or even misleading. Before instructing an expert, therefore, it is essential to consider a number of questions which appear below: The Need for Expert Evidence Sometimes the need for expert evidence will be obvious. If the defence case is alibi and the Crown put the defendant’s DNA at the scene, a defence expert will of course be required to scrutinise the accuracy of those findings. The party calling the evidence will have to consider whether, leaving to one side the tactical advantages of calling the evidence, it meets the basic requirements of relevance and admissibility. The justification for calling expert evidence is that it relates to a matter which falls outside the experience and knowledge of the jury. If it does not and if the jury can form its own conclusions without help, the evidence is unnecessary and thereby inadmissible. (e.g. is a witness telling the truth? Normally a jury can be relied on to reach an opinion. The position may be different if the witness suffers from a mental disability). The next issue to consider is whether the proposed expert is qualified to give such evidence. Resolution of this question is not limited to an analysis of his credentials, but extends to whether his specialism is sufficiently well recognised to have attained a basic level of reliability (see facial mapping, voice recognition, lip reading and Low Copy Number DNA). Usually, however, the relevance and admissibility of the expert evidence in question will not be in issue. Of greater significance will be the decision as to whether or not it should be used. The Decision to Call Expert Evidence As with any other type of evidence, the decision whether to call an expert or not will be based on a risk/reward analysis of the benefits of doing so. The most well qualified people often make bad witnesses; anybody can look good on paper. Generally the risks of calling a questionable expert can be avoided by choosing someone of pre-eminence in his field, with a track record of giving respected and balanced expert evidence. That way, quacks and charlatans can be avoided, as can those experts who insist on giving evidence in a manner incomprehensible to any ordinary member of the public. If all these pitfalls have been successfully avoided and an appropriate expert instructed, the next issue to consider will be the scope of the evidence he can give. The Scope of the Expert Enquiry In any given case, the judge will direct the jury that they are not bound by the opinions given by experts called on either side, and that the factual issues are for them to determine. Experts have increasingly been encouraged to make findings which go to the ‘ultimate issue’ i.e. ‘guilty or not guilty’. Frequently, for example, in fraud cases, an expert accountant will be called by the Crown to say that, in his view, there can be no rational, honest explanation for the transactions under consideration. This tendency to give an opinion on the ultimate issue has extended into homicide as much as any other field. It is important, however, that the experts are not permitted to overstep the mark. Plainly, a fingerprint expert is entitled to say that the ridge characteristics on a gun are such as to leave no doubt that the mark was left by the defendant’s left ring finger. What he is not entitled to say, however, is that this identifies the defendant as the gunman. The Extent of the Remaining Evidence If there is no other evidence apart from, for example, a particle of gunshot residue (see R v Barry George) it is unlikely that the case will ever come to trial. If there are many different strands of evidence, each supporting the other, then the evidence may be admissible and the weight or strength of the evidence will be for the jury to decide. Similar considerations apply when the bulk of the evidence comprises conflicting opinions from experts on both sides. It has been held that if the outcome of the trial depends exclusively, or almost exclusively, on a serious disagreement between distinguished and reputable experts, it will often be unsafe to proceed. The next issue will be how best to present the expert evidence at trial. Presentation of the Evidence Unfortunately, this is the stage at which problems arise. The task of solicitor and counsel in calling such a witness, therefore, is to ensure that the subject matter can be understood by a jury. This can only be achieved by attaining a sound understanding of the subject matter oneself by having a conference with the expert well in advance of trial. Any opinion given must be backed up with reasons justifying the view taken. Once mastered, the information must be presented in a way that the jury understands. This means the avoidance of jargon (an abrasion is a graze and a suture is a stitch). You should employ user-friendly material for the jury (e.g. graphics packs and PowerPoint presentations). Presenting one’s own case is, however, only half the battle. The time will come when it is necessary to challenge the expert evidence called by the other side. Cross Examination Often, particularly when defending, the key will be to cross-examine swiftly, rather than getting bogged down in protracted debate or skirmishes around the fringes. Once experts are allowed off the leash, they can be difficult to control and can make matters worse. Always make sure you have your own expert there to ensure that you are not blinded with science. Conclusion The scope of topics which can be covered by experts is infinitely varied. The purpose of calling such evidence is to elicit opinion evidence capable of establishing the facts or inferences it is sought to prove. The key to the successful use of experts lies in both their proper selection and deployment. Picking suitably qualified, properly briefed and presentable experts represents only a promising start. This has to be backed up by hard work from the legal team to ensure that they properly understand the issues, such that the evidence can be presented in a persuasive and comprehensible fashion. If achieved, the evidence will be compelling. If not, it can badly backfire. When in doubt, it is often better not to call a defence expert at all and merely rely on cross-examination. Orlando Pownall QC is one of the most formidable and sought after advocates practising at the criminal bar, in courts up to and including the House of Lords/Supreme Court. Darryl Lockwood is a Criminal Defence Lawyer within Switalskis Solicitors Serious Crime team.
Posted on: Wed, 24 Sep 2014 14:34:48 +0000
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